EP1361781A1 - Electronic ballast for operating discharge lamps - Google Patents

Abstract

The arrangement has a converter with a charge pump for improving power factor and a pump control switch that carries a pump suppression current if at low impedance, resulting in an effective reduction in charge pump operation, has temperature-dependent resistance and is heated by the suppression current to a switching temperature at which the resistance adopts values that reduce the suppression current so charge pump operation is not degraded. The arrangement has a converter (A,HT,T1,T2) with a charge pump (D5,D6,C31,C41,C51) for improving the power factor and a pump control switch that carries a pump suppression current if it is in a low impedance state, resulting in an effective reduction in charge pump operation. The pump control circuit resistance is temperature-dependent so that it is heated to a switching temperature by the pump suppression current at which the resistance adopts values that reduce the suppression current so that the operation of the charge pump is no longer degraded. AN Independent claim is also included for the following: (a) a method starting and operating a discharge lamp.

Description

Technical field

The invention relates to a circuit arrangement according to the preamble of Claim 1. It is in particular a circuit arrangement that can be used in an operating device for gas discharge lamps, the Invention disadvantages in the ignition of gas discharge lamps eliminated with the use of a charge pump to improve the power factor.

State of the art

Circuit arrangements for gas discharge lamps, hereinafter referred to as lamps for short, which are operated on a mains voltage which has, for example, an effective value for the voltage of 230 V and a frequency of 50 Hz, generally contain a rectifier and an inverter. Such circuit arrangements are subject to relevant standards regarding the mains current harmonics and thus the power factor (eg IEC 1000-3-2), which requires additional circuitry. A cost-effective way to comply with these standards is through circuit topologies, which are called charge pumps in the literature. A detailed description of the mode of operation and of exemplary embodiments can be found, for example, in the following literature: Qian J., Lee FC: Charge Pump Power-Factor-Correction Technologies, Part I: Concept and Principle, Part II: Ballast Applications , IEEE Transactions on Power Electronics , Vol. 15, No. 1, pp 121-139, New York, USA,

Power Electronics, Vol. 15, No. 1, pp 121-139, New York, USA, 2000. The principle A charge pump consists of the mains voltage during a first half period a high-frequency oscillation that is significantly higher than the mains frequency, Extract energy, store it temporarily in a pump element and during a second half period to a storage capacitor. So that's it possible to achieve an approximately sinusoidal course of the mains current and thus values for the mains harmonics and the power factor achieve as required in the standards.

As long as the charge pump is in operation, it continuously supplies energy to the storage capacitor from. This energy is in normal operation, i.e. H. while the lamp burns, removed from the lamp. A state of equilibrium develops, which is expressed in a constant mean value of the voltage across the storage capacitor, where the mean is to be formed over half a network period. At the ignition The lamp requires a high voltage on the lamp, but it takes Do not light up energy in this state. Because the charge pump is running energy supplies to the storage capacitor, the voltage across the storage capacitor rises during the ignition of the lamp. So bump used in the circuit arrangement Components u. U. to their load limit. In particular components as the storage capacitor itself and electronic used in the circuit arrangement Switches are made with the lowest possible maximum for cost reasons Voltage load designed. With a lamp that is hesitant or even does not ignite, there is therefore a risk of destruction of the circuit arrangement, since the voltage at the storage capacitor is the maximum permissible voltage of components exceeds. This danger is with circuit arrangements that do not Preheat the electrode filaments of the lamp, increased. By preheating of the electrode filaments is the voltage necessary for ignition Lamp reduced and thus the ignition process shortened. With circuit arrangements, The ignition process is longer if the electrode coils are not preheated and with it the tension higher, which during the ignition on Storage capacitor builds up. Devices that contain such circuitry are also called cold start devices. Good lighting lamps are lamps with them the ignition process is completed after 1ms. Lamps that ignite badly Ignition process is completed after 1ms. Lamps that ignite badly sometimes up to 100ms for the ignition.

To a circuit arrangement with charge pump before being destroyed by a not to secure or poorly igniting lamp, it is common for the circuit arrangement to be equipped with a shutdown. The shutdown is usually monitors the voltage at the storage capacitor. If the value of the Voltage at the storage capacitor above a predetermined switch-off value, the Circuit arrangement deactivated. So there’s the problem that especially in the case of cold start devices, the operation of lamps that last a long time Have ignition process is not ensured.

In the prior art, a pump control switch is used to solve this problem proposed about the closed, d. H. low resistance state, a pump suppression current flows. The pump control switch is state of the art designed as an electronic switch, for example as a MOSFET. The pump suppression current essentially causes the pump element to the storage capacitor not only provides energy, but can also withdraw energy and thus the charge pump is limited in its functionality or completely out of operation is set. The charge pump generally contains the series connection a first and a second pump diode. This series connection is between the Mains voltage and the storage capacitor switched. The connection point of the The high-frequency oscillation is applied to the pump diode via the pump element. The pump control switch becomes parallel to the series connection of the pump diodes connected.

In principle, the functionality of the charge pump is also possible suppress that a switch is arranged in series or parallel to the pump element becomes. As a rule, however, a pump element has no function in the charge pump also has other influences and functions in the circuit arrangement this option was not used in practice.

It is also possible that the charge pump is not just a series connection of

Contains pump diodes, but several series circuits connected in parallel Pump diodes, their respective connection points via different pump elements be subjected to high-frequency vibration. In this case there is the charge pump from several so-called pump branches. Through the pump control switch all pump branches are affected equally.

In US 5,396,153 (Shackle) the pump control switch is from a Control device that controls the value of the voltage across the storage capacitor supervised. The control device compares the value of the voltage across the storage capacitor with a predetermined threshold and switches the pump control switch when the threshold is exceeded, causing the charge pump to stop operating is set.

In US 5,986,408 (Langeslag), the pump control switch is from a Controlled control device that monitors the ignition of the lamp. As long as the Has not ignited, the pump control switch is closed and thus the Charge pump out of order.

In both prior art writings, in addition to the pump control switch an effort to control it is driven.

Presentation of the invention

It is an object of the present invention to provide a circuit arrangement according to the Provide the preamble of claim 1, the increase with little effort of the value of the voltage on the storage capacitor prevented during ignition.

This object is achieved by a circuit arrangement with the features of the preamble of claim 1 by the features of the characterizing part of the claim 1 solved. Particularly advantageous configurations can be found in the dependent ones Claims.

According to the invention, the pump control switch is not an electronic one Switch that has a control input from a control device must be operated. Rather, it is the pump control switch according to the invention around a device that is driven by the pump suppression current a heating time is heated. Reaches the pump control switch according to the invention a given switching temperature, its resistance increases, causing the pump suppression current is reduced and the charge pump is effective becomes. The pump control switch according to the invention advantageously does not require any Control device, as is the case in the prior art. Automatically suppressed during the heating process, the functionality of the charge pump and prevents an increase in the value of the voltage at the storage capacitor during this time. The heating-up time is such that even a poorly igniting lamp is safe can be ignited. If the lamp did not ignite after the heating-up time, then so is it a defective lamp or is there another fault and the circuit arrangement must be taken out of operation. This can be done through a Shutdown happen, the value of the voltage across the storage capacitor supervised. It is crucial that this switch-off device is not used to control the Charge pump serves, but intervenes only in the event of a fault. The invention Pump control switch requires no control device for its control and thus offers a cost-effective option for poorly igniting lamps to ignite with circuit arrangements containing a charge pump.

So-called PTC thermistors are preferred for the pump control switch according to the invention used in the literature also as PTC (Positive Temperature Coefficient) be designated. When the circuit arrangement is started up, the PTC thermistor a temperature at which he has a resistance whose value is so low is that an effective pump suppression current can flow. Through this The PTC thermistor is heated up by pump suppression current. Naturally, PTC thermistors have a non-linear relationship between temperature and resistance. Accordingly, there is a switching temperature described above. Reaches the PTC thermistor this switching temperature so its resistance rises to values that none effective pump suppression current flow more and thus the charge pump can work as intended. The loss line in the PTC thermistor, the Switching temperature and the thermal inertia of the PTC thermistor are according to the invention coordinated so that the switching temperature is reached after a time, which is sufficient to ignite a poorly igniting lamp.

In principle, a thermistor (NTC) can also be used to control the charge pump are connected, for example, in series with the pump element. In doing so, however on the one hand, the disadvantages already listed above, on the other hand, the Non-linearity of thermistors is not so pronounced that there is a clear one Forms switching temperature. This is not how the charge pump works reliably reproducible.

The pump control switch according to the invention is preferred in parallel with the series connection of the pump diodes switched. To rectify the mains voltage a generic circuit arrangement a rectifier, which in general consists of rectifier diodes arranged in a bridge circuit. From the Literature is known that the task of the pump diode facing the mains voltage can also be taken over by rectifier diodes. From the series connection in this case, the pump diode is only the one facing the storage capacitor Pump diode accessible. The pump control switch according to the invention is in this case connected in parallel to this pump diode.

For charge pumps with multiple pump branches, it may be desirable to to influence the pump control switch only one pump branch. For example, this is then advantageous if one to ignite the lamp over the Peak value of the mains voltage increased voltage is necessary. For effective reduction the pump control switch according to the invention becomes the mode of operation of a pump branch connected in parallel to the pump diode to the relevant pump branch heard and facing the storage capacitor.

Brief description of the drawings

Figur 1

ein Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung

Figur 2

ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung

Figur 3

ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung

Figur 4

ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung

The invention will be explained in more detail below on the basis of exemplary embodiments with reference to drawings. Show it:

Figure 1

an embodiment of a circuit arrangement according to the invention

Figure 2

a further embodiment of a circuit arrangement according to the invention

Figure 3

a further embodiment of a circuit arrangement according to the invention

Figure 4

a further embodiment of a circuit arrangement according to the invention

In the following, transistors are identified by the letter T, diodes by the letter D, capacitors by the letter C, chokes by the letter L, potentials denoted by the letter P followed by a number. Also below are for the same and equivalent elements of the different Embodiments used the same reference numerals throughout.

Preferred embodiment of the invention

A circuit arrangement according to the invention is shown in FIG. At the input terminals J 1 and J2 is provided to connect a mains voltage, which in a filter device F is fed. The filter device F serves for suppression of radio interference. The output of the filter device F is with a Rectifiers consisting of diodes D1, D2, D3 and D4 connected. The diodes D1-D4 are connected in a known bridge rectifier circuit. About the Diodes D1 and D3 become the positive potential of the rectified at a potential P1 Mains voltage provided. A ground potential M is with the Diodes D2 and D4 connected. The series connection is between P1 and a potential P2 a first pump diode D5 and a second pump diode D6. The polarity of the pump diodes is chosen so that the mains voltage in the circuit arrangement can generate a current flow. Between the potential P2 and A storage capacitor C1 is connected to ground potential M.

The voltage at C1 feeds an inverter, which is described below. Between P2 and the ground potential M is the series connection of a first and of a second semiconductor switch T1 and T2, which is a so-called half-bridge form. The potential P4 forms at the connection point of the semiconductor switches. In the example, the semiconductor switches are designed as MOSFETs. However, you can can also be designed, for example, as bipolar transistors or IGBTs. T1 and T2 are alternately controlled at the gates by a half-bridge driver HT. A control circuit A specifies the clock of this control. This can be yours Generate clock independently or depending on output variables of the half-bridge. in the the latter case is called a self-excited half-bridge inverter. The Functioning of such an inverter is for example in the document EP 781 077 (Schmitt) explains. Is between the potential P4 and a potential P5 a lamp inductor L1 switched. The series connection between P5 and P2 is one Lamp Lp and a coupling capacitor C51 switched. The high frequency vibrations at P4 and P5 become the connection point via capacitors C31 and C41 of the pump diodes D5 and D6, where the potential P3 is formed. In the present case, C31 and C41 form the pump elements.

According to the invention, parallel to the series connection of the pump diodes D5 and D6 PTC thermistor switched. As long as it is cold, P3 flows in at a low potential Pump suppression current from P2 via the PTC thermistor KL and via D5. Thereby the functioning of the charge pump consisting of the elements D5, D6, C31 and C41 effectively reduced and a steady increase in the voltage at the storage capacitor is avoided during the ignition process. By the pump suppression current the PTC thermistor heats up. If it reaches a switching temperature, so his resistance rises sharply. The current at P3 over low potential the PTC thermistor flows is then compared to the current drawn from the mains voltage becomes negligible. The functioning of the charge pump is no longer effectively impaired. In the exemplary embodiment from FIG. 1, the high-frequency oscillation exploited at P4 and at P5 for the charge pump. It is also possible, to use only one of the two high-frequency vibrations. The capacitor that with the unused high-frequency oscillation can then be coupled to P2 become.

Another possible variation is that the pump diodes D5 and D6 are not looped into the positive output of the rectifier, but into the negative. In this case, the ground potential M via the series connection of the Pump diodes with the negative output of the rectifier, i.e. the connection point of diodes D2 and D4.

1. Als Hochfrequenzschwingung für die Ladungspumpe wird nicht mehr das Potenzial an P4 und P5 benutzt. Vielmehr wird die Hochfrequenzschwingung des Stroms durch den Koppelkondensator C52 für die Ladungspumpe benutzt. C52 ist demnach nicht mehr mit P2, sondern mit der Anode von D6 verbunden. Als Pumpelement wirkt nun C52. C32 ist mit P2 verbunden und C42 ist parallel zur Lampe Lp geschaltet.

2. Die Pumpdiode D5 ist gegenüber dem Ausführungsbeispiel aus Figur 1 entfallen. Ihre Funktion wird von den Gleichrichterdioden D1 und D3 übernommen. Damit fällt das Potenzial P1 mit dem Potenzial P3 zusammen. Erfindungsgemäß ist der Kaltleiter KL parallel zur Pumpdiode D6 geschaltet. Seine Funktionsweise ist analog zum Ausführungsbeispiel aus Figur 1.

A further example of a circuit arrangement according to the invention is shown in FIG. There are two changes compared to the exemplary embodiment from FIG. 1:

1. The potential at P4 and P5 is no longer used as the high-frequency oscillation for the charge pump. Rather, the high frequency oscillation of the current through the coupling capacitor C52 is used for the charge pump. C52 is therefore no longer connected to P2, but to the anode of D6. C52 now acts as the pump element. C32 is connected to P2 and C42 is connected in parallel to the lamp Lp.

2. The pump diode D5 is omitted compared to the embodiment of Figure 1. Their function is taken over by the rectifier diodes D1 and D3. The potential P1 thus coincides with the potential P3. According to the invention, the PTC thermistor KL is connected in parallel to the pump diode D6. Its mode of operation is analogous to the exemplary embodiment from FIG. 1.

The two changes between Figure 1 and Figure 2 are not coupled, but can be done independently. This applies equally for all variations of the charge pump known from the literature.

FIG. 3 shows a further exemplary embodiment of a circuit arrangement according to the invention shown. Compared to the embodiment of Figure 1, the Circuit arrangement now two pump branches. Parallel to the pump diodes D5 and D6 is a further series circuit made up of pump diodes D7 and D8. The Capacitors C33 and C43 are not connected at one end compared to FIG. 1. Only the capacitor C33 is connected to the potential P3. in the The second pump branch is the high-frequency oscillation of the potential P5 over the Capacitor C43 fed to potential P6, which is the junction of the pump diodes D7 and D8 of the second pump branch designated.

According to the invention, the PTC thermistor KL is only parallel to the pump diode D6 of the first Pump branch switched. This only influences the first charge pump in a targeted manner. The second charge pump is also active during the ignition. This can be desirable be to a higher voltage on the storage capacitor during the ignition process To achieve C1 and thus the ignition voltage is increased.

It is also possible for the PTC thermistor KL to be connected in parallel with the pump diode D8. In this case, the second pump branch becomes ineffective until the PTC thermistor heats up connected.

Claims (6)

Circuit arrangement for operating discharge lamps (Lp) on a mains voltage, with the following features: Inverters (A, HT, T1, T2), with a charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53) to improve the power factor, Pump control switch (KL) which, when in a low resistance state, carries a pump suppression current, which effectively reduces the operation of the charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53 ) has the consequence characterized in that the resistance value of the pump control switch (KL) is so temperature-dependent that the pump suppression current heats the pump control switch to a switching temperature at which the resistance of the pump control switch assumes values that reduce the pump suppression current in such a way that the functioning of the charge pump (D5-D8 , C31, C32, C33, C41, C42, C43, C51, C52, C53) is no longer effectively impaired. Circuit arrangement according to claim 1, characterized in that the pump control switch (KL) contains a PTC thermistor. Circuit arrangement according to claim 1 or 2, characterized in that the charge pump contains two pump diodes (D5, D6, D7, D8) connected in series and the pump control switch (KL) is connected in parallel with the series connection of the pump diodes. Circuit arrangement according to claim 1 or 2, characterized in that the charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53) two series-connected pump diodes (D5, D6, D7, D8) contains, which are connected between the mains voltage and a storage capacitor (C1) and the pump control switch (KL) is connected in parallel to the pump diode (D6, D8), which is coupled to the storage capacitor (C1) Circuit arrangement according to claim 1 or 2, characterized in that the charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53) contains several pump branches with pump diodes (D5-D8), at least one of which is connected in parallel to a pump control switch (KL). Method for starting and operating a discharge lamp (Lp) with a circuit arrangement comprising an inverter (A, HT, T1, T2) with a charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53) for improving the power factor and a pump control switch (KL) contains characterized by the following steps: Connecting the circuit arrangement to a mains voltage, a pump suppression current flows through the pump control switch (KL), which effectively affects the functioning of the charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53), the pump suppression current heats the pump control switch (KL), the temperature of the pump control switch (KL) reaches a switching temperature, at the switching temperature, the resistance value of the pump control switch (KL) increases, the pump suppression current is reduced by the increased resistance value of the pump control switch (KL), the pump suppression current drops to a value which no longer represents an effective impairment of the functioning of the charge pump (D5-D8, C31, C32, C33, C41, C42, C43, C51, C52, C53).

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